Dispersal of Philaenus spumarius (Hemiptera: Aphrophoridae), a Vector of Xylella fastidiosa, in Olive Grove and Meadow Agroecosystems.

The introduction of the Xylella fastidiosa Wells bacterium into Apulia (South Italy) has caused the massive dieback of olive trees, and is threatening olive production throughout the Mediterranean Region. The key vector of X. fastidiosa in Europe is the spittlebug Philaenus spumarius L. The dispersal capabilities of P. spumarius are poorly known, despite being a key parameter for the prediction of the spread of the bacterium. In this study, we have examined the dispersal of P. spumarius adults in two different agroecosystems in Italy: an olive grove in Apulia (Southern Italy) and a meadow in Piedmont (Northern Italy). Insects were marked with albumin and released during seven independent trials over 2 yr. The recapture data were pooled separately for each agroecosystem and used to estimate the dispersal kernels of P. spumarius in the olive grove and in the meadow. The diffusion coefficient estimate for P. spumarius was higher in the meadow than in the olive grove. The median distance from the release point for 1 d of dispersal was 26 m in the olive grove and 35 m in the meadow. On the basis of our model, we estimated that 50% of the spittlebug population remained within 200 m (98% within 400 m) during the 2 mo period of high abundance of the vector on olives in Apulia. The dispersal of P. spumarius is thus limited to some hundreds of meters throughout the whole year, although it can be influenced to a great extent by the structure of the agroecosystem.

Biology and Prevalence in Northern Italy of Verrallia aucta (Diptera, Pipunculidae), a Parasitoid of Philaenus spumarius (Hemiptera, Aphrophoridae), the Main Vector of Xylella fastidiosa in Europe.

The meadow spittlebug, Philaenus spumarius (L.) (Hemiptera Aphrophoridae), the main vector of Xylella fastidiosa Wells et al. in Europe, has few known natural enemies. The endoparasitoid Verrallia aucta (Fallén) (Diptera, Pipunculidae) was first noticed a long time ago but very little is known about its biology and prevalence. In this study, the presence and prevalence of V. aucta were investigated in different regions of northern Italy, both in plain-foothill and montane zones. Parasitic larvae were identified by the dissection of spittlebug adults, P. spumarius and Neophilaenus campestris (Fallén), and by a new species-specific molecular tool targeting the ITS2 and COI genomic regions, developed in this work. A small-scale rearing was set up to gain information on the life cycle of V. aucta on its main host P. spumarius. During the four-year investigation (2016-2019) the pipunculid parasitoid displayed low prevalence, reaching a maximum parasitization rate of 17.5% (calculated over the adult spittlebug season) in vineyards of the Piemonte region. Over the whole period, no significant difference in the prevalence was found between male and female spittlebugs. Collected data and rearing observations suggest that V. aucta is monovoltine and synchronous with P. spumarius, laying eggs in newly emerged adults, developing as an endoparasitoid through two larval stages during the whole summer, and overwintering as a pupa in the soil.

Biological characterization of Euscelidius variegatus iflavirus 1.

Virus-based biocontrol technologies represent sustainable alternatives to pesticides and insecticides. Phytoplasmas are prokaryotic plant pathogens causing severe losses to crops worldwide. Novel approaches are needed since insecticides against their insect vectors and rogueing of infected plants are the only available strategies to counteract phytoplasma diseases. A new iflavirus, named EVV-1, has been described in the leafhopper phytoplasma vector Euscelidius variegatus, raising the potential to use virus-based application strategies against phytoplasma disease. Here transmission routes of EVV-1 are characterized, and localization within the host reveals the mechanism of insect tolerance to virus infection. Both vertical and horizontal transmission of EVV-1 occur and vertical transmission was more efficient. The virus is systemic and occurs in all life-stages, with the highest loads measured in ovaries and first to third instar nymphs. The basic knowledge gained here on the biology of the virus is crucial for possible future application of iflaviruses as biocontrol agents.

High Resolution Assessment of Spatio-Temporal Changes in O2 Concentration in Root-Pathogen Interaction.

Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. lycopersici (Fol), is one of the most destructive soil-borne diseases of tomatoes. Infection takes place on the roots and the process starts with contact between the fungus and the roots hairs. To date, no detailed studies are available on metabolic activity in the early stages of the Fol and tomato root interaction. Spatial and temporal patterns of oxygen consumption could provide new insights into the dynamics of early colonization. Here, we combined planar optodes and spatial analysis to assess how tomato roots influence the metabolic activity and growth patterns of Fol. The results shows that the fungal metabolism, measured as oxygen consumption, increases within a few hours after the inoculation. Statistical analysis revealed that the fungus tends to growth toward the root, whereas, when the root is not present, the single elements of the fungus move with a Brownian motion (random). The combination of planar optodes and spatial analysis is a powerful new tool for assessing temporal and spatial dynamics in the early stages of root-pathogen interaction.

Key Impact of an Uncommon Plasmid on Bacillus amyloliquefaciens subsp. plantarum S499 Developmental Traits and Lipopeptide Production.

The rhizobacterium Bacillus amyloliquefaciens subsp. plantarum S499 (S499) is particularly efficient in terms of the production of cyclic lipopeptides, which are responsible for the high level of plant disease protection provided by this strain. Sequencing of the S499 genome has highlighted genetic differences and similarities with the closely related rhizobacterium B. amyloliquefaciens subsp. plantarum FZB42 (FZB42). More specifically, a rare 8008 bp plasmid (pS499) harboring a rap-phr cassette constitutes a major distinctive element between S499 and FZB42. By curing this plasmid, we demonstrated that its presence is crucial for preserving the typical physiology of S499 cells. Indeed, the growth rate and extracellular proteolytic activity were significantly affected in the cured strain (S499 P-). Furthermore, pS499 made a significant contribution to the regulation of cyclic lipopeptide production. Surfactins and fengycins were produced in higher quantities by S499 P-, whereas lower amounts of iturins were detected. In line with the increase in surfactin release, bacterial motility improved after curing, whereas the ability to form biofilm was reduced in vitro. The antagonistic effect against phytopathogenic fungi was also limited for S499 P-, most probably due to the reduction of iturin production. With the exception of this last aspect, S499 P- behavior fell between that of S499 and FZB42, suggesting a role for the plasmid in shaping some of the phenotypic differences observed in the two strains.

Complete genome sequence of Bacillus amyloliquefaciens subsp. plantarum S499, a rhizobacterium that triggers plant defences and inhibits fungal phytopathogens.

Bacillus amyloliquefaciens subsp. plantarum S499 is a plant beneficial rhizobacterium with a good antagonistic potential against phytopathogens through the release of active secondary metabolites. Moreover, it can induce systemic resistance in plants by producing considerable amounts of surfactins. The complete genome sequence of B. amyloliquefaciens subsp. plantarum S499 includes a circular chromosome of 3,927,922bp and a plasmid of 8,008bp. A remarkable abundance in genomic regions of putative horizontal origin emerged from the analysis. Furthermore, we highlighted the presence of genes involved in the establishment of interactions with the host plants at the root level and in the competition with other soil-borne microorganisms. More specifically, genes related to the synthesis of amylolysin, amylocyclicin, and butirosin were identified. These antimicrobials were not known before to be part of the antibiotic arsenal of the strain. The information embedded in the genome will support the upcoming studies regarding the application of B. amyloliquefaciens isolates as plant-growth promoters and biocontrol agents.